Alfred joined the Royal Navy on 7 Feb 1897 as a boy sailor. He signed for 12 years from the age of 18. He was about 5'2.5" tall with dark brown hair and grey eyes when he joined the Royal Navy and he had a birthmark on the back of his right leg. He was a Chatham based rating. His postings throughout his career were as follows:
HMS Impregnable 7 Feb 1897 to 12 Feb 1897 (Devonport Training Establishment)
HMS Lion 12 Feb 1897 to 5 Aug 1898 (Devonport Training Ship)
HMS Agincourt 5 Aug 1898 to 13 Oct 1898 (Portsmouth Training Ship)
HMS Magnificent 14 Oct 1898 to 30 Jun 1899 (Battleship)
HMS Pembroke I 1 Jul 1899 to 5 Sep 1899 (Chatham Shore Base)
HMS Furious 6 Sep 1899 to 2 Jul 1901 (Cruiser)
HMS Pembroke3 Jul 1901 to 1 Sep 1901 (Chatham Shore Base)
HMS Excellent 2 Sep 1901 to 15 Mar 1902 (Portsmouth Shore Base)
HMS Pembroke I 16 Mar 1902 to 20 Mar 1902 (Chatham Shore Base)
HMS Wildfire 21 Mar 1902 to 23 Apr 1902 (Sheerness Gunnery School)
HMS Pembroke 24 Apr 1902 to 5 Jun 1902 (Chatham Shore Base)
HMS Fantome 6 Jun 1902 to 12 Nov 1904 (Sloop) ^[1]
HMS Pembroke I 13 Nov 1904 to 28 Feb 1905 (Chatham Shore Base)
HMS Wildfire 1 Mar 1905 to 5 Jul 1905 (Yacht/Flagship)
HMS Pembroke 6 Jul 1905 to 14 Jul 1905 (Chatham Shore Base)
HMS Ramillies 15 Jul 1905 to 28 Jul 1905 (Battleship)
HMS Pembroke 29 Jul 1905 to 31 Jul 1905 (Chatham Shore Base)
HMS Resolution 1 Aug 1905 to 7 May 1906 (Battleship)
HMS Triumph 8 May 1906 to 31 Aug 1906 (Battleship)
HMS Pembroke 1 Sep 1906 to 23 Oct 1906 (Chatham Shore Base)
HMS Shearwater 24 Oct 1906 to 6 Nov 1908 (Sloop)
HMS Pembroke I 7 Nov 1908 to 10 Dec 1909 (Chatham Shore Base)
HMS Charybdis 11 Dec 1909 to 1 Aug 1910 (Cruiser)
HMS Pembroke I 2 Aug 1910 to 15 Aug 1910 (Chatham Shore Base)
HMS Blenheim 16 Aug 1910 to 14 Aug 1912 (Cruiser)
HMS Pembroke 15 Aug 1912 to 20 Jan 1913 (Chatham Shore Base)
HMS Blenheim 21 Jan 1913 to 30 Sep 1913 (Cruiser)
HMS Egmont 1 Oct 1913 to 4 May 1914 (Ironclad Frigate - Depot ship in Malta)
HMS Blenheim (Grasshopper) 5 May 1914 to 30 Sep 1915 (Depot Ship) ^[2]
HMS Pembroke II (Grasshopper) 1 Oct 1915 to 24 Nov 1915 (Chatham Shore Base)
HMS Blenheim (Grasshopper) 25 Nov 1915 to 24 Aug 1917 (Depot Ship)
HMS Pembroke I 25 Aug 1917 to 10 May 1918 (Chatham Shore Base)
HMS Boadicea 11 May 1918 to 14 Jul 1918 (Cruiser)
HMS Gunner (???) 15 Jul 1918 to 18 Dec 1918 (??)
HMS Attentive III (???) 19 Dec 1918 to 19 Dec 1918 to 10 Jan 1919 (Depot Ship))
HMS Attentive III (Haldon) 11 Jan 1919 to 28 Feb 1919 (Minesweeper)
HMS Attentive III (Doncaster) 1 Mar 1919 to 27 Jul 1919 (???)
HMS Tyne (Doncaster) 28 Jul 1919 to 31 Dec 1919 (???)
HMS Pembroke 1 Jan 1920 to 7 Jul 1921 (Chatham Shore Base)
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He became an Ordinary Seaman on his 18th birthday on 5 Apr 1899 and was promoted to Able Seaman on 1 Dec 1900. He was then promoted quite quickly to Leading Seaman in Apr 1904 and then Petty Officer on 11 May 1904. He achieved the rate of Acting Chief Petty Officer on 1 Mar 1917 and eventually, full Chief Petty Officer in 1918.

His character was recorded as VG Superior throughout his career.
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^[1] In December 1902 the, when Alfred was part of the crew, Fantome was one of a combined Anglo-German fleet which established a blockade of the Venezuelan coast. These retaliatory measures were undertaken on account of outrages on British ships and subjects for which no satisfaction could be obtained. Nine Venezuelan gunboats of the fleet were taken to sea and sunk. President Castro immediately imprisoned all British and German subjects, but was forced to release them by the American Consul. A British merchant ship was seized by the mob Puerto Cabello, but two ships at once proceeded to the place, and having released the ship, bombarded the fort. After an eight weeks’ blockade, in which the British and the German vessels divided the coast, the Venezuelans consented to arrangements which brought the blockade to a conclusion. A small force also assisted in the blockade.
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^[2] During the wartime years, Alfred was drafted first of all to HMS Blenheim between May 1914 and Sep 1915. Former Canadian Prime Minister Sir Charles Tupper died in England in 1915 and was repatriated to Halifax by Blenheim. The Blenheim served as a destroyer depot ship and it looks as if Alfred was assigned to the destroyer HMS Grasshopper up until 1917. The Grasshopper was initially a coastal destroyer but had been converted into a torpedo boat. She was involved in the Dardanelles campaign.
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We can see Alfred in 1901 living in Kent:
Alfred John Knibbs Crew Single 19 Able Seaman Windsor Berks
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Alfred is seen in 1911 at Tendring in Essex, at a location listed as Military. I believe this was probably HMS Ganges.
Military Knibbs Alfred John b.1882 29 Tendring Essex